1. Field of the Invention
The present invention relates to methods for friction welding. More particularly, the present invention relates to a method and device for frictionally welding certain types of metal and metal alloy components.
2. Discussion of Background
Friction welding is a welding method, particularly suited for rotationally symmetrical objects, in which one or both of the objects to be welded are rotated at a predetermined speed. The two objects are then brought together under high pressure, or upset, to forge the materials together. One form of friction welding, inertial welding, varies slightly in procedure. Instead of using a constant speed motor drive to provide rotation, a flywheel attached to the rotational machine's spindle stores kinetic energy and disperses that energy to the weld interface when axial force is applied. The high pressure, or upset, involved in bringing these two objects together causes the displacement of metal from the two objects, called weld flash, which normally forms on the outside of the welded object. The weld flash is usually machined off, however, its removal sometimes results in defective welds.
Friction welding techniques and equipment are not new. Several U.S. patents detail various aspects of friction welding. U.S. Pat. No. 3,144,710 issued to Hollander, et al. describes several friction welding arrangements. Several issued U.S. patents describe flash traps, which are modifications in the structure of one or both of the welded objects that assist in providing a better weld by urging the weld flash toward a desirable location or away from an undesirable location. U.S. Pat. No. 4,832,769 issued to Shantz, et al. discusses the use of a flash trap to keep flash from an area that is subsequently modified mechanically to provide a better welded seal. U.S. Pat. No. 3,618,196 issued to Sluetz describes a technique using two successive welds to completely seal a particular portion of the weld flash in a rectangular flash trap internal to the final welded structure. Several other issued U.S. patents describe the friction welding of specific articles or friction welding methods adapted to particular environments.
None of the previously issued patents teach flash traps that are designed specifically to cause almost all of the weld flash to flow inwardly in order to achieve a completely sealed weld. This type of result is desired in applications where machining off external weld flash results in unacceptable welds. There exists a distinct need for an internal flash trap designed to assist in providing a superior welding seal by urging almost all of the weld flash internally, therefore all but eliminating external weld flash.